The present application relates to an image-taking apparatus and a method thereof. More specifically, the image-taking apparatus and method thereof of the present application allow obtaining of a plurality of images under different illumination conditions, and is applicable to apparatuses for performing biometric authentication by taking an image of a portion of a living-body, such as fingerprints, finger veins or palm veins.
A method for taking an image of finger veins of a living-body in the direction towards the ball of a finger, under the condition where the back of the finger is substantially perpendicularly illuminated, has been proposed (refer to, for example, Japanese Unexamined Patent Application Publication No. 2004-49705).
FIG. 1 is a schematic diagram depicting an example of the method for taking an image of the finger veins in the direction towards the ball of the finger under the condition where the back of the finger is substantially perpendicularly illuminated by infrared LEDs used as an illumination light source, as disclosed in Japanese Unexamined Patent Application Publication No. 2004-49705.
In this case, infrared LEDs 1, 2 and 3 are used as the illumination light source, and further, in the direction towards the ball of the finger, which is an object OBJ, an image made of light rays transmitted through the finger, which result from emission of light rays by the illumination light sources, is taken by an image-taking device 4.
Moreover, a method for taking an image of the finger veins of a living-body in the direction towards the ball of the finger, under the condition where the side surface of the finger is substantially perpendicularly illuminated, has been proposed (refer to, for example, Japanese Unexamined Patent Application Publication No. 2006-95056).
Further, a method for taking an image of the finger veins of a living-body in the direction towards the ball of the finger, under the condition where the ball of the finger is substantially perpendicularly illuminated, has been proposed (refer to, for example, Japanese Unexamined Patent Application Publication No. 2004-49705).
FIG. 2 is a schematic diagram depicting an example of the method for taking an image of the finger veins in the direction towards the ball of the finger under the condition where the ball of the finger is substantially perpendicularly illuminated by infrared LEDs used as an illumination light source, as disclosed in Japanese Unexamined Patent Application Publication No. 2004-49705.
In this case, a plurality of LEDs, the number of which is two in the example shown in FIG. 2, used as the illumination light source, are located at the side of the image-taking device 4, and an image made of light rays transmitted through the object OBJ, which is the finger of the living-body, which result from reflection of light rays inside the finger, is taken by the image-taking device 4.